In an opening of a bag, a slide fastener is widely used to open and close the bag. As a type of this slide fastener, a two-way slide fastener where two sliders are disposed in a fastener chain to face each other with head alignment or tail alignment is known. In the two-way slide fastener, even though the two sliders are slid in either a forward direction or a backward direction along element rows, the fastener chain can be opened and closed.
As teeth that are attached to the two-way slide fastener, the metallic one-side teeth are used. If the metallic one-side teeth are used, a two-way slide fastener that is strong in rigidity against horizontal pull force, has a metal glossy surface, and is excellent in design can be obtained. As a shape of the metallic one-side tooth, an interlock convex portion is formed on one surface of an interlock head portion and an interlock dent portion is formed on the other surface.
Meanwhile, in a two-way slide fastener that uses general metallic one-side teeth, when one slider is slid and the metallic one-side teeth are interlocked or the interlocked metallic one-side teeth are released from an interlock state, sliding movement resistance is small and the sliding movement of the slider can be smoothly performed. For example, when the other slider is slid and the metallic one-side teeth are released from the interlock state, even though sliding movement resistance becomes slightly higher than sliding movement resistance at the time of sliding movement in one slider, the interlocked metallic one-way teeth can be smoothly released.
However, when the metallic one-side teeth are interlocked by the other slider, the sliding movement resistance increases and the slide fastener cannot be smoothly opened and closed.
This reason is considered as follows. When the metallic one-side teeth are interlocked, the metallic one-side teeth are interlocked while an outside edge of an interlock dent portion comes into colliding contact with an interlock head portion of the interlocked counterpart-side tooth. For this reason, the sliding movement of the slider is not smoothly performed.
In order to prevent the outside edge of the interlock dent portion and the interlock head portion of the interlocked counterpart-side tooth from coming into colliding contact with each other, shapes of the metallic one-side teeth are variously suggested. As an example of the metallic one-side teeth, the present applicant already suggests metallic one-side teeth that are formed by a forming apparatus of teeth for a slide fastener (refer to Patent Document 1) or teeth for a slide fastener (refer to Patent Document 2).
The metallic one-side teeth that are described in Patent Document 2 are metallic one-side teeth that are obtained by improving the metallic one-side teeth formed by the forming apparatus described in Patent Document 1. In drawings of Patent Document 2, the configuration of a feature portion of the metallic one-side teeth described in Patent Document 1 is also shown. The configuration of the feature portion of the metallic one-side teeth that can be formed by the forming apparatus described in Patent Document 1 will be described using a cross-sectional view and a perspective view of the metallic one-side teeth described in Patent Document 2.
FIG. 5 is a cross-sectional view showing an interlock head portion of the metallic one-side tooth described in Patent Document 2 and FIG. 6 is a main portion perspective view showing the interlock head portion of the metallic one-side tooth described in Patent Document 2. In the metallic one-side tooth described in Patent Document 1, an inclined plane 37 is formed in a front end wall of an interlock head portion 33 at the side of an interlock dent portion 35.
FIGS. 5 and 6 illustrate a second conventional example of the invention.
First, the case where two interlock head portions 33b and 33c are interlocked will be described using FIG. 5. FIG. 5 shows a state where the interlock head portion 33b is beginning to interlock with the interlock head portion 33a which is already interlocked with the other metallic one-side tooth, and the interlock head portion 33c is about to interlock with the interlock head portion 33b. 
When a slider (not shown in the drawings) is slid and the two interlock head portions 33b and 33c are interlocked with each other, an inclined plane 37b is formed in a front end wall 36b of the interlock head portion 33b to prevent an interlock head portion 34c to be interlocked and the front end wall 36b of the interlocked interlock head portion 33b from being interlocked while coming into sliding contact with each other. Likewise, in the interlock head portions 33a and 33c, inclined planes 37a and 37c are formed in front end walls 36a and 36c of the interlock head portions 33a and 33c to prevent the front end walls from coming into colliding contact with counterpart-side interlock convex portions performing interlocking.
FIG. 5 shows a state where an interlock convex portion 34b formed in the interlock head portion 33b passes through a region of the inclined plane 37a formed in the front end wall 36a of the interlock head portion 33a and is inserted into the interlock dent portion 35a. 
As shown in FIG. 6, if the inclined plane 37 is formed in the front end wall 36 of the interlock head portion 33, sliding movement resistance of the slider at the time of interlocking can be decreased and sliding movement of the slider can be smoothly performed. If the metallic one-side teeth that are formed by the apparatus described in Patent Document 1 are used in a two-way slide fastener, slidability of the slider when the metallic one-side teeth are interlocked can be improved.
However, even in the case where the metallic one-side teeth that are formed by the apparatus described in Patent Document 1 are used in a two-way slide fastener, when horizontal pull force is applied to the two-way slide fastener after interlocking, the horizontal pull force is applied to an opening edge 39 in the interlock dent portion 35 of the metallic one-side tooth shown in FIG. 6. Since the inclined plane 37c is formed in the front end wall 36 of the interlock head portion 33, the thickness of the opening edge 39 of the interlock dent portion 35 is configured to be small.
For this reason, if moment based on the horizontal pull force is applied to the opening edge 39 of the interlock dent portion 35 where the thickness decreases, the bending amount in the opening edge 39 may increase. If the opening edge 39 is greatly bent, slidability of the slider may be deteriorated.
The metallic one-side tooth that is described in Patent Document 2 is a metallic one-side tooth that is obtained by improving the metallic one-side tooth, such that the bending amount in the opening edge 39 decreases, even when the moment based on the horizontal pull force is applied to the opening edge 39 of the interlock dent portion 35. In the metallic one-side tooth that is described in Patent Document 2, as shown in FIG. 6, a rib 38 is formed on an inner side of the front end wall 36 of the interlock head portion 33.
By the rib 38 formed on the inner side of the front end wall 36 of the interlock head portion 33, rigidity in the opening edge 39 is enhanced. If the rigidity in the opening edge 39 is enhanced, the bending amount in the opening edge 39 decreases. If the bending amount in the opening edge 39 is decreased, slidability of the slider can be greatly improved.
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 58-116946
Patent Document 2: Japanese Utility Model Application Publication (JP-Y) No. 1-22505